I need some electrical help

[canuck750]

I am getting my Eldorado ready for the trip to John Day this coming week, I had the fenders and bags repainted and once everything was back together I noticed I don't have a brake light.

I have tested every wire, fitted water proof disconnects for the bags, new wires, replaced the brake / running light bulb, Just wasted 4 hours with no results.

This is what I do know, the running light on the Wixom bas work fine, both front and read signal lights work fine. Head light is working on high and low.

The running light will come on but the brake light is very, very weak. Brake light does not come on when I use the front brake lever (converted to dual disc with micro switch in the master cylinder.

When I swap the rear tail light brake and running light wires the light gets super bright but no difference when I press the rear brake pedal.

I am wondering if I have a ground problem to the rear light?? Sorta came to me now that I have left the project for Monday night to tackle. The ground is set to a Wixom rear bag bracket and maybe that's just not a good enough ground.

I also pulled the wire from the front brake switch off and when I did that I get the faint brake light when pressing the rear pedal. With the front brake lead connected past the rear brake switch I get the full on bright light all the time.

I need to have a brake light to head off to Oregon, its probably something real simple that I have overlooked, electricity is one great big mystery to me!!!

Thanks

Jim

[rodekyll]

I always tell folks to start at the ground and work up.  I think you've given yourself the same best advice.

Jumper from + to the brake contact and see if the bulb lights up directly.  Then do the same thing from the downstream side of the switches.  This will tell you if the wiring to the rear fender is good.

Check the brake switches with a test light on either side.  I don't remember if they switch the hot or ground side, but you'll figure that out soon enough.  Check that the switches pass juice.

But I think you'll find your problem is at ground level.

When do you take off?

[canuck750]

Thanks RK!

Heading out Wednesday morning with my buddy Harold on his V11 Sport, stopping in Calgary for some quick tuning of Harold's bike Wednesday morning then on to BC. We will be in John Day Friday morning, was hoping to leave sooner but damn work commitments for Tuesday.

PS the rotor cover is packed

[Tom H]

Depending on the foot brake switch you have, some versions the plunger was hot and unless insulated from the activating lever it would short out normally blowing a fuse.

With that said, look for a corrosion issue in the bulb socket, fuse block, switch and connectors. If I remember right, the hand brake switch was wired to the foot brake switch's terminals. Maybe take a good look at the fit of the connector to the fuse block.

Good luck,
Tom

[rodekyll]

Got it fixed yet?

Where are you crossing the border?

[Antietam Classic Cycle]

Is the taillight an original CEV unit? Several times I've had the problem of the bulb socket not making contact with the taillight housing, even though it all seemed crimped together tightly. No contact between the socket and housing = no ground. I simply soldered the bulb socket to the housing on the outside (where the wires go into the taillight) and it worked properly after that.

[canuck750]

Is the taillight an original CEV unit? Several times I've had the problem of the bulb socket not making contact with the taillight housing, even though it all seemed crimped together tightly. No contact between the socket and housing = no ground. I simply soldered the bulb socket to the housing on the outside (where the wires go into the taillight) and it worked properly after that.

Thanks Charlie, yes the tail light is an original CEV round style unit, I will check the ground. I think I will run a dedicated ground from where the battery ground connects to the transmission support all the way to the tail light and see what effect that has. This problem is, I think, similar to the tail light ground issue I had on the 750S3, relying on the ground to find its way through the flip up rear fender to the frame. I think I moved the tail light ground from where it was before I reinstalled the fenders and bags.

RK,

I plan on crossing at Eastport or Porthill

[rodekyll]

I believe Idahorider is in eastport.

I'll be coming down the west route.  You're gonna get hot.

If you have the time to find an LED bulb this would be a good time yo upgrade that oem tail light bulb.

[Kiwi_Roy]

Plus one on the LED, this will take most of the strain off any hard working switches as it only draws a fraction of the current.
Solder it in as it will never need changing.

If the front brake switch refuses to work just add a bit of foot until you get it sorted.

I'm sure it's a ground problem as David says. if you can see a tiny bit of the bulb base touch it with a grounded wire while working the brake.

http://www.thisoldtractor.com/guzzi007/schematics/1973_V850_USA.gif
One other possibility is loss of 12 volts at the top side of the brake switch (17) the pointy fuses don't make great contact, monitor either side of the switch to chassis with a test light, one side should be full On and not dim when you brake the other side should be Off and come full On when you brake.

If all else fails just don't stop till you get there

[canuck750]

If all else fails just don't stop till you get there

I may need you to diagnose the problem if I am forced to run cannonball the whole way!

[John A]

When you get it fixed and do the final wireing, put a simple relay on the brake light circuit . Makes the switches last longer and you get full voltage to the light.

[canuck750]

Finally, problem(s) solved... turns out it was not one thing but three, thanks to RK and Kiwi Roy for your advice.

First after jumping the two rear brake switch terminals there was nothing, pulled the switch, no power get through, the terminals are loose in the plastic housing, drilled out the rivets and its cracked and the plunger does not engage the brass tangs, junk, only lasted 44 years! I tried several auto shops, no luck with anything remotely close, robbed a switch off my project eldo but it wasn't much better but it should hold for now.

The front brake switch was barely plugged in, fixed the connections.

Ran a separate ground from the frame to the back tail light and low and behold it all works.

Fitted a LED tail light bulb and life is good.

After a shake down the speedo craps out, oh well who needs a speedo anyways.